Dry working black image compositions



United States Patent 3,493,376 DRY WORKING BLACK IMAGE COMPOSITIONSHarry L. Fichter, Jr., Lakewood, Ohio, assignor to HorizonsIncorporated, a Division of Horizons Research Incorporated, acorporation of Ohio No Drawing. Filed Oct. 18, 1966, Ser. No. 587,429Int. Cl. G03c 1/52 US. Cl. 96-90 6 Claims ABSTRACT OF THE DISCLOSURE Aphotosensitive composition comprising an organic halogen compound, atriphenylmethane leuco compound, a substituted skatole, and asubstituted indole.

This invention relates to photosensitive compositions from which a blackor near neutral image is obtained as a direct printout or as the resultof the application of heat to said composition after it has beenphotographically exposed. More particularly, it relates tophotosensitive compositions having improved photographic speed ascompared with prior art compositions and which have totally dry workingcharacteristics.

Photosensitive compositions which are believed to be based on freeradicals are described in a large number of patents and patentapplications and in technical articles published by HorizonsIncorporated and a list of issued United States patents is appendedbelow for the purpose of incorporating their disclosures herein, byreference.

Some of the listed patents and publications describe free radicalphotographic systems which are dry fixing, i.e. in which the imageobtained after exposure is fixed and rendered insensitive to light bytotally dry means. Others of the listed patents and publicationsdescribe free radical photographic systems which yield a black image ornear neutral image.

A specific object of this invention is to provide a dry workingphotographic composition yielding a black or near neutral image as adirect printout or as the result of the application of heat to saidcomposition after it has been photographically exposed and particularlyto compositions having a greatly improved photographic speed as comparedwith prior art compositions having totally dry working characteristics.

With the exception of color photographic printing or where as specificcolored image is desired for display purposes, virtually every practicalapplication of the above noted free radical photographic systems prefera black or near black image color. Such contemplated uses include:office photocopy; microfilm retrieval systems; photographic printing,e.g. portraiture proofing; and even such military uses as themultigeneration aerial reconnaisance printing described in PS&E, vol.IX, No. 2, pp. 133-137, 1965; and all such uses demand a suitable blackimage produced without recourse to wet processing.

UNITED STATES PATENTS Photographic Science and Engineering, volume 5,Number 2, March-April 1961, pages 98-103.

Photographic Science and Engineering, volume 8, Number 2, March-April1964, pages 91-95.

3,493,376 Patented Feb. 3, 1970 Photographic Science and Engineering,volume 8, Number 2, March-April 1964, pages -103.

Photographic Science and Engineering, volume 9, Number 2, March-April1965, pages 133-137.

The neutral image dry working characteristics of the compositions hereindescribed are particularly important in certain of the above uses sincethe use of a wet working system in high speed aircraft or space vehiclesis almost inconceivable. One such use whose feasibility has beenestablished is the preparation of multigeneration printing of aerialreconnaissance negatives as described in the above noted publication.When a military reconnaissance aircraft photographs a target, thenegative resulting from that photograph is developed and reproducedthrough as many as four generations for determination of theintelligence revealed in the photograph. The original negative isprinted only once and then is stored in the archives. All subsequentprints are made from the second generation prepared from the orginalnegative. Conventional silver halide systems are not completely suitablefor this multigeneration printing purpose, since the image is granular(particulate) and consequently each subsequent generation losesinformation which may be valuable in strategic decisions made from theuse of these photographs. Free radical photo-systems being molecularrather than granular have almost unlimited resolution particularly whencoated in thin layers, (about 4 to 5 microns thick), to take advantageof the geometry of present printer processors and their light sources.Free radical photographic systems have been established to be anexcellent medium for these multigeneration aerial reconnaissanceprinting, especially photosensitive free radical compositions based onthe teachings of United States Patent 3,109,736 and described inPhotographic Science and Engineering, vol. IX, No. 2, pp. 133-137, forMarch and April 1965 under the title of New Photographic Processes, No.4, the Cyanine Base Free Radical PhotosystemA Panchromatic Black ImageHigh Resolution Printout Film. The compositions described yieldexcellent jet black images and retain high latitude multigenerationprinting through four generations, with the minimum loss ofintelligence. However, the compositions are not dry working, but requirea solvent rinse after exposure to render the image fixed and stable toambient light.

Photointerpreters who evaluate these aerial reconnaissance photographstraditionally have been schooled in the use of black image materials andare reluctant to use other colors; hence the need for a dry workingblack image system to be used for aerial reconnaissance multigenerationprinting.

One preferred composition in accordance with the present invention is asfollows:

Pliolite-S-SA 15% in methylene chloride cc 300 The composition isprepared by bringing the several constituents together in a suitablesolvent system under a safelight or in total darkness and, afterthoroughly mixing the composition, applying it to a solid substrate suchas baryta paper or a film of polyester, glass or other suitable support.

After the composition has been laid down as a thin film, it is permittedto dry in air, in the dark or under a safelight, and then it isphotographically exposed to the equivalent of 1.4 watt seconds/cm? andheat fixed for minutes at 135 C.150 C. in moving air, whereby a verystable dense black image was observed in the exposed areas. With thisamount of exposure, maximum density of about 1.0 is achieved and theheated film is completely fixed, i.e. the image and background do notchange upon further exposure to light.

While not Wishing to be bound by any specific explanation as to thefunction of each of the several constituents, it is believed that threeconstituents contribute to the formation of a black or near neutralimage when acted on by the products which result when the iodoform isexposed to a suitable dose of radiant energy, namely the triphenylmethane compound, the S-methoxyskatole, and the 2,5-dimethylindole, eventhough the 4,4,4"-tri(p-toluidino)-triphenylmethane when photolyzedalone in the presence of a halogen activator gives brilliant blueimages, S-methoxyskatole when photolyzed with a halogen activator givesa brownish-black image, and dirnethylindole when photolyzed with ahalogen activator gives a pink image.

The function of the 4-picoline-N-oxide in the composition appears to bethat of an organic oxidizing agent which acts as a speed promoter inthese systems containing leuco compounds.

The triphenylstibine and 2,6-di-t-butyl-p-cresol appear to act asstabilizers and prevent oxidation or degradation of the color formersduring the exposure and the subsequent heating of the composition whenin the form of a photosensitive film. The use of these compounds isdescribed in other issued patents and/or co-pending patent applicationsfiled on behalf of the applicants assignee.

The thioacetamide in the composition is for the purpose of providing adarker color when the triphenylmethane component is converted to itscolored form.

The indole-3-carboxaldehyde appears to hasten the formation of thecolored product when the indole compounds, in this case,5-methoxyskatole and 2,5-dimethylindole, are photolyzed in the presenceof the activator, as described in United States Patent 3,164,467 notedabove.

Binders for these compositions can be chosen from any one of a number ofbinders described in the patents already issued on free radicalphotographic compositions. Polystyrene, polyvinyl chloride,styrene-acrylonitrile copolymers, ethyl cellulose, both G type and Ntype, cellulose acetate butyrate, polyvinyltoluene, butadiene-styrenecopolymers, the copolymer of polyvinyl chloride and vinyl isobutylether, have all been used successfully in the practice of thisinvention. The choice of binder, however, produces considerablevariation in photographic speed and image color. All of the foregoingbinders give a neutral to black image.

Various substitutions may be made in the above formulation withoutdeparting from the intended scope of the invention.

For instance, instead of polystyrene in benzene, other film formingbinders can be used. Particularly preferred are polystyrene withmolecular Weights above 100,000 (e.g. about 223,000) and abutadiene-styrene copolymer sold as Pliolite-S5A (Goodyear ChemicalCo.).

Further, instead of triphenylstibine, other triaryl compounds may beused, such as triphenylarsine, phosphine or bismuthine, as described inUnited States Patent 3,275,443 issued Sept. 27, 1966, to Eugene Wainer.

Similarly, it is possible to use other organic halogen compounds asdescribed in U.S. Patent 3,042,515 issued July 3, 1962, to EugeneWainer, instead of the preferred iodoform.

Other color formers have been used in place of the three compounds aspreferred. For example, leuco opal blue is a suitable replacement for4,4',4-tri(p-toluidino)- triphenylmethane in these compositions,however, less background stain is observed after heat fixing with4,4',4"- tri(p-toluidino)-triphenylmethane than is normally observedwith leuco opal blue. Other leuco compounds taken from thetriphenylmethane class of dyestuffs such as leuco crystal violet, leucomalachite green work equally well in these compositions, except that theresulting color is not black.

Finally, it should be noted that although the proportions given in thepreceding example are believed to give optimum results for the specifiedconstituents, the percentage of the individual constituents can bevaried over a considerable range, depending in some instances on thesolubility of the specific ingredient and in others on the nature andamount of the other compounds present in the formulation and on theresults desired.

With the formulation given above, proportions which have been foundsuitable are as follows:

4,4,4-tri (p-toluidino -triphenylmethane grams- 2 to 104-picoline-N-oxide mg 50 to 1000 Triphenylstibine g 0.1 to 102,6-di-t-butyl-p-cresol g 1 to 5 Idoform g 10 to 50 5 -methoxyskatole g2 to 10 Thioacetamide mg to 500 2,5 -dimethylindole g 2 to 10Indole-3-carboxaldehyde g 0.1 to 10 With formulations within the abovepercentages, a range of exposure of from 0.05 to 5.0 Watt seconds/ persquare centimeter have been found to be quite adequate. Exposures ofmore than 5 watt seconds/per square centimeter appear to amount tooverexposure and to give some fog build-up.

With other ingredients substituted in the above, or with other relativeproportions, the range of exposure may be readily determined from asensitivity curve made with calibrated monochromatic exposures in amanner known in the art.

Having now described a preferred embodiment of this invention, it is notintended that it be limited except as may be required by the appendedclaims.

I claim:

1. A photosensitive composition comprising: an organic halogen compoundhaving at least three halogen atoms attached to a terminal carbon atom;a mixture of colorless light sensitive color forming constituents inproportions which yield a near neutral or black image when reacted withthe products resulting from the photolytic exposure of said organichalogen compound, wherein the light sensitive constituents in saidmixture are a triphenyl methane leuco compound, a substituted skatole,and a substituted indole; and a support for said composition.

2. The composition of claim 1 wherein the light sensitive color formingconstituents are 4,4,4"-tri(p-toluidino)- triphenylmethane,S-methoxyskatole and 2,5-dimethylindole.

3. The composition of claim 1 including in addition at least oneadditional compound which enhances the formation of the resulting image,and is selected from the group consisting of: 4-picoline-N-oxide;triphenylstibine; di-tbutyl-p-cresol; thioacetamide; and indole3-carboxaldehyde.

4. The composition of claim 1 wherein the constituents are 4, 4,4''-t1'i p-toluidino -triphenylmethane grams 2 to 10 4-picoline-N-oxide mg50 to 1000 Triphenylstibine g 0.1 to 10 2,6-dit-butyl-p-cresol g l to 5Iodoform g 10 to 50 S-methoxyskatole g 2 to 10 Thioacetamide mg 100 to500 2,5-dimethylindole g 2 to 10 Indole-3-cat'boxaldehyde g 0.1 to 10 5.The composition of claim 1 wherein the constituents are 4,4',4"-tri(p-toluidino -triphenylmethane gm 5 4-picoline-N-oxide rng 5 00Triphenylstibine gm 1 2,6-di-t-butyl-p-cres0l gm 2.5 Iodoform gm 20S-methoxyskatole "gm 5 Thioacetamide mg 300 2,5 -dimethylindole gm 5Indole-3-carboxaldehyde -gm- 1 Acetone cc 100 Benzene cc 100P1ioliteS-5A 15% in methylene chloride cc 300 6. A dry workingphotographic process which comprises preparing composition of claim 1 ina thin film; exposing said composition to a pattern of radiant energy,

3,164,467 1/1965 Sprague et al 969O 3,275,443 9/1966 Wainer 96-90FOREIGN PATENTS 723,124 12/1965 Canada.

NORMAN G. TORCHIN, Primary Examiner I. R. HIGHTOWER, Assistant ExaminerUS. Cl. X.R. 9665, 88

